01 - Preheat the oven to 375°F (190°C). Line a mini muffin pan with paper liners or lightly grease each cup.
02 - In a large mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, salt, and ground cinnamon until uniformly blended.
03 - Add cold, cubed unsalted butter to the flour mixture. Using a pastry cutter or your fingertips, incorporate the butter until the mixture forms coarse crumbs.
04 - In a medium bowl, whisk together whole milk, egg, and vanilla extract until smooth.
05 - Pour the wet mixture into the bowl of dry ingredients. Stir gently with a spatula until just combined, ensuring not to overmix the batter.
06 - Using a small cookie scoop or tablespoon, portion the dough into the mini muffin pan, filling each cup about three-quarters full.
07 - Transfer the pan to the oven. Bake for 13 to 15 minutes, until the tops are lightly golden and a toothpick inserted into the center emerges clean.
08 - While baking, combine 1/3 cup granulated sugar and 1 teaspoon ground cinnamon in a small bowl to make the coating.
09 - Allow bites to cool in the pan for 5 minutes. Using a pastry brush, coat each bite with melted butter and roll in the cinnamon sugar mixture until evenly coated.
10 - Serve warm or at room temperature for optimal flavor and texture.